The present invention relates to a system for reproducing a disc.
A disc reproducing system having an automatic disc changer has recently become popular. The disc reproducing system is provided with a rack wherein a large number of CDs are stored so as to improve the storing efficiency of the CDs.
FIG. 26 is a perspective view of such a reproducing system disclosed in Japanese Patent Laid Open 9-223351 which has been filed by the present patent applicant.
FIGS. 27 and 28 show another reproducing system disclosed in Japanese Patent Laid Open 59-104759.
The system of FIG. 24 will be described firstly. A disc reproducing system is provided with a roulette device 3 mounted on a chassis base 2 in a housing. The housing comprises the chassis base 2, casing 8, rear panel 9 and the front operation panel 10. The roulette device 3 comprises a base 3a, rack base 3b having a spindle 3c and a center pole 5 mounted on the spindle 3c, and five rotary circular racks 4a, 4b, 4c, 4d and 4e, each having a center hole 4 in which the center pole 5 is engaged. Hence, all of the racks 4a to 4e are securely mounted on the center pole 5 in a tiered formation.
In each of the racks 4a to 4e, there is formed radial slits 40 in each of which a recording medium D such as CD can be stored. A radial recess 41 through which a disc player 7 provided adjacent the racks 4a to 4e passes is further formed in each of the racks 4a to 4e at a predetermined circumferential position. In the player 7, an arm 7a is provided for taking out one of recording mediums D. The arm 7a is operated by a driving device (not shown) upon loading and ejecting of the recording mediums D into and out of the disc player 7 thereby passing through one of the slits 40 of the rack from the underneath thereof.
The front operation panel 10 is provided with an opening 10a through which the recording mediums D is inserted and taken out. The opening 10a is covered by a door 6 having a pin 6a projected downward from the top. The pin 6a engaged with the upper end of the center pole 5 so that the door 6 is rotatably mounted thereon. The door 6 is rotated on the pole 5 in the counterclockwise direction to disclose the racks 4a to 4e through the opening 10a. 
On the underside of the rack 4a, an encoder (not shown) and photo sensors are provided for detecting position of a desired recording mediums on one of the racks 4a to 4e. 
When a select button on the operation panel 10 is operated to select a desired recording mediums, the racks 4a to 4e are rotated and stored at an angular position where the desired recording medium is stored. The disc player 7 is vertically moved to the position of one of racks where the recording medium is stored. The arm 7a takes out the recording medium and loads it on the disc player 7, thereby reproducing the recording medium.
Referring to FIGS. 27 and 28, an annular storing base 12 is rotatably provided in a frame 11 and rotated by a rotating device 13. On the storing base 12, a plurality of recording mediums D are stored. An information reading and writing device 15 and an arm driving device 17 for driving an arm 16 are mounted on a holding base 14. A guide 15a is provided for guiding the recording medium D. An opening 18 is formed for inserting the recording medium D. The arm 16 has pawls 16a and is driven by a screw 19.
When a desired recording medium D is selected, the storing base 12 is rotated so that the selected recording medium is positioned at the opening 18 of the information reading and writing device 15. Then, the arm 16 is moved in the direction X by the arm driving device 17, and inserts the recording medium D into the device 15. The recording medium D is located at a position d shown by dotted lines. At the position, the information is read and written.
Thereafter, the information reading and writing device 15 moves the recording medium D to a position where a part of recording medium D is projected from the opening 18.
A detector (not shown) mounted on the arm 16 detects whether the recording medium D contacts with the arm 16 or not. If contacts, the pawls 16a are moved in the direction Y in FIG. 27 by solenoids (not shown) to grip the recording medium D. If does not contact, the arm 16 is moved in the direction X until contacts. Then, the arm 16 is moved in the direction Xxe2x80x2 so that the recording medium D is returned to the storing base 12, and hence the sequential operation is completed.
FIG. 29 shows an example of a rotating mechanism of the disc reproducing system. In the rotating mechanism 20, a shaft 22 is secured to a frame 21 at the upper end thereof, and to a base 23 at the lower end thereof. On the shaft 22, a disc holder 24 is rotatably mounted. A plurality of discs D are radially arranged and supported on a disc receiver 24a of the disc holder 24.
The disc holder 24 has a toothed periphery 24b with which a pinion 25 is engaged.
The disc holder 24 is rotated by a motor through the pinion 25 so as to position a selected disc to a reproducing device (not shown).
In the system of FIG. 26, it is necessary to provide a device for preventing the center pole 5 from vibrating. If the center pole 5 vibrates, the position of the desired disc may not be exactly detected.
In the system shown in FIGS. 27 and 28, it is also necessary to provide a vibration preventing device of the rotating device 13 in order to exactly load a disc. However, it is difficult to provide such a device for the rotating device 13.
The device of FIG. 29 has following problems.
(1) In the rotating device 20 having five degrees of freedom at the shaft 22 and one degree of freedom at the pinion 25, it is important that the shaft 22 is kept vertical, because the vibration of the shaft causes the peripheral position to largely fluctuate.
(2) Since the driving pinion 25 having a small diameter engages with teeth of disc holder having a large diameter, there is a case where the pitch of the teeth changes about 0.8 mm by change of ambient temperature.
(3) The deflection of the disc holder renders the operation relative to the driving mechanism including the driving pinion 25 defective.
(4) Since the shaft 22 is disposed in the center of the disc holder 24, no devices can be provided in the central portion of the disc holder.
In order to resolve above described problems, a rotating mechanism 20xe2x80x2 shown in FIG. 30 has been proposed.
The rotating mechanism 20xe2x80x2 comprises a base 27, an annular disc holder 28 having a disc receiver 28a and a toothed periphery 28b and a driving pinion 29 engaged with the toothed periphery 28b. 
On the underside of the disc holder 28, an annular projection 28c is formed. The annular projection 28c is mounted on a plurality of rotating rollers 30 rotatably mounted on the base 27, so that the disc holder 28 is rotatably mounted on the base 27 about the axis Z. Thus, the disc holder 28 is positioned in the Z, X and Y axes by the roller 30.
In order to mount a large number of discs on the disc holder, there is a disc holder having an inside diameter of 200 mm.
Such a large disc holder causes the following problems.
(1) In order to precisely manufacture the disc holder, the manufacturing cost increases.
(2) It is difficult to produce the disc holder having a high preciseness.
An object of the present invention is to provide a disc reproducing system in which a rotating shaft is prevented from vibrating.
According to the present invention, there is provided a system for reproducing a disc comprising, a base, a disc holder for holding a plurality of discs, supporting means for rotatably mounting the disc holder on the base, guiding means provided between the disc holder and the base for guiding the disc holder so as to be rotated about an axis, rotating means for rotating the disc holder so as to position a desired disc to a predetermined position, a reproducing device for reproducing the desired disc, carrying means for carrying the desired disc between the predetermined position and the reproducing device.
The guide means comprises an annular groove and a plurality of projections engaged with the annular groove and the supporting means comprises a plurality of rollers which are annularly mounted on the base.
The disc holder has an annular shape in plan view. The annular groove is provided on underside of disc holder and the projections are mounted on the base, each of which has a cylindrical shape.
The rotating means includes a rack formed on an inside periphery of the disc holder, and a drive gear engaged with the rack.
One of the projections is disposed near an engaging point where the driving gear engages with the rack, and another projection is disposed on a line perpendicular to a line connecting said axis with the engaging point.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.